The present invention relates to a design apparatus for automatically designing a jig comprising a plurality of components. Such a jig is used for clamping and guiding the work of welding, assembling, clamping, cutting or the like or tools therefor. This design apparatus is related to an automatic design apparatus which employs a computer system or the like, i.e., CAD/CAM. The components which form the jig include parts which are commercially available and widely used and special parts which can be exclusively used in the jig.
When a jig comprising a plurality of components is designed, conventional design support systems called CAD/CAM generally use the following design methods:
When a workpiece to be designed comprises a plurality of parts, the graphic data base for each of the parts substantially corresponds to the actual shape of each part. For example, when a part is basically characterized by length.times.width.times.height ratio, the graphic data thereof has the same length.times.width.times.height ratio. In the graphic data base are previously registered the graphic data for each of the parts and graphic data for the sam parts in various configurations. The graphic form displayed is therefore equivalent to the graphic data of the part designated even if a part to be selected and the configuration of the same part to be selected are designated by the operator or by using a program. In other words, graphic forms other than the graphic forms stored in the graphic data base are never displayed.
For example, Japanese Patent Laid.Open No. 63-137219 discloses a technique for automatically designing a mold, but the above.described fact also applies to this technique of this Japanese Patent Laid-Open with respect to the graphic forms displayed in the system of this prior art.
However, parts having any forms cannot be designed by CAD/CAM, and the part designed must always satisfy certain given conditions. For example, when a jig is automatically designed, a jig having any desired forms cannot be designed. The jig designed should be limited by the type of workpiece for which the jig is used and the position and the form of the surface which contacts with the jig. In addition, since a jig is always moved and contains a movable portion, the jig must not interfere with other portions of the workpiece. When a jig is designed, therefore, consideration must be given to not only the contact surface but also the general form of the workpiece. Namely, it is necessary to strictly limit the conditions for designing only one jig. Further, jigs which do not satisfy these strictly limited conditions are useless as jigs.
The above.described conventional CAD/CAM is, however, designed so that the operator or programmer can draw lines or select the parts registered in an interactive manner, as described above. The system has only the function to draw lines in accordance with the designation from the operator or extract from the data base the graphic data directly corresponding to the registered part selected and display it. When a jig which does not satisfy the limited conditions is consequently designed, therefore, the operator is placed in a situation in which the work of designing must be started all over again for the purpose of designing a useful jig.
This causes an increase in the time required for designing and is thus significantly inefficient. If an attempt is made to reduce the time for designing, the operator or the programmer must imagine the graphic form displayed to some extent before giving instructions to draw lines or instructions to select a part, elaborate on the instructions and the selection by controlling and selecting in one's head and endeavor as much as possible to designate an accurate part form. However, since there are various kinds of limits, it is extremely difficult to imagine the graphic form of the whole of the part on the assumption of these limited conditions. This finally leads to a reduction in the efficiency of the work.